Synthesis and reactivity of monomeric magnesium and zinc silyl compounds ToMM–Si(SiHMe2)3 and ToMM–Si(SiMe3)3 are described (ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The magnesium compounds react slowly with water and air, while the zinc compounds are inert. With CO2, ToMMg–Si(SiHMe2)3 provides ToMMgO2CSi(SiHMe2)3 through CO2 insertion, whereas ToMZn–Si(SiHMe2)3 affords ToMZnOCHO.